The Collaborative International Dictionary of English v.0.48:

Extortionate \Ex*tor"tion*ate\, a.
   Characterized by extortion; oppressive; hard.
   [1913 Webster]

WordNet (r) 3.0 (2006):

extortionate
    adj 1: greatly exceeding bounds of reason or moderation;
           "exorbitant rent"; "extortionate prices"; "spends an
           outrageous amount on entertainment"; "usurious interest
           rate"; "unconscionable spending" [syn: exorbitant,
           extortionate, outrageous, steep, unconscionable,
           usurious]